#include <stdio.h>
#include <math.h>

//https://www.nowcoder.com/practice/0f5d9bfcd63b47fda2052a583b1fbd1f?tpId=107&&tqId=33308&rp=1&ru=/ta/beginner-programmers&qru=/ta/beginner-programmers/question-ranking

int main() {
    float r = 0;
    double v = 0;
    scanf("%f", &r);
    v = 3.1415926 * 4 / 3 * pow(r, 3);
    printf("%.3f", v);
    return 0;
}
